Methods for gas sensing with single-walled carbon nanotubes

Abstract

Methods for gas sensing with single-walled carbon nanotubes are described. The methods comprise biasing at least one carbon nanotube and exposing to a gas environment to detect variation in temperature as an electrical response.

The invention claimed is: 
     
       1. A sensing method comprising:
 providing at least one carbon nanotube; 
 biasing the at least one carbon nanotube; 
 exposing the at least one carbon nanotube to an environment where gas is adapted to be detected, whereby, in presence of the gas, heat is removed by the gas from the at least one carbon nanotube; 
 varying pressure inside the environment with the gas, whereby temperature of the at least one carbon nanotube changes with variation of pressure; and 
 detecting variation in temperature of the at least one carbon nanotube as an electrical response. 
 
     
     
       2. The method of  claim 1 , wherein the method is a gas sensing method. 
     
     
       3. The method of  claim 1 , wherein the method is a chemical species sensing method to differentiate chemical species. 
     
     
       4. The method of  claim 1 , wherein each one of the at least one carbon nanotube is a single-walled carbon nanotube. 
     
     
       5. The method of  claim 1 , wherein biasing the at least one carbon nanotube occurs by connecting electrodes at end regions of the at least one carbon nanotube. 
     
     
       6. The method of  claim 5 , wherein the at least one carbon nanotube and the electrodes are suspended and devoid of a substrate. 
     
     
       7. The method of  claim 6 , wherein suspension occurs through critical point drying. 
     
     
       8. The method of  claim 5 , wherein the electrodes comprise metals selected from the group consisting of Al, Ti, Nb, Mo, Pd, Pt, Sc, Ta, W, Hf, Zr, Au, Cr and combinations thereof. 
     
     
       9. The method of  claim 5 , wherein the electrodes comprise metals selected from the group consisting of Au, Cr and combinations thereof. 
     
     
       10. The method of  claim 6 , wherein the electrodes comprise electrodes made of Cr. 
     
     
       11. The method of  claim 1 , wherein varying the pressure inside the environment with the gas comprises varying the pressure from a substantially ambient pressure to a substantially vacuum pressure. 
     
     
       12. The method of  claim 1 , wherein the variation in the temperature of the at least one carbon nanotube causes a resistance change in the at least one carbon nanotube, the resistance change being detected as a current response. 
     
     
       13. The method of  claim 1 , wherein the environment is a chamber containing the gas and the carbon nanotube. 
     
     
       14. The method of  claim 1 , wherein the at least one carbon nanotube is an array of carbon nanotubes. 
     
     
       15. The method of  claim 1 , wherein the at least one carbon nanotube is a bundle of carbon nanotubes. 
     
     
       16. The method of  claim 1 , wherein the at least one carbon nanotube is voltage biased and the electrical response is a current response. 
     
     
       17. The method of  claim 1 , wherein the electrical response is a voltage response.